The present invention relates to methods for welding. In particular, the present invention relates to methods of welding metal parts, such as parts for aerospace and aviation applications, with the use of laser welding techniques.
In gas turbine engines, it is important to cool the turbine airfoils to preserve the integrity of the airfoil structure and also to attain high engine performance by operating the turbine at optimum temperature levels. It is also important to avoid utilizing more cooling air than is necessary to minimize the overall penalty that occurs with the use of engine air for purposes other than generating thrust or horsepower.
One method of optimizing the use of cooling air is to employ meter plates to restrict the flow entering into the blade roots of each of the airfoils. Meter plates are typically secured to the blade roots of the airfoils with laser seam welding operations. To ensure that the meter plates remain secured to the blade roots during engine operation, the welds between each meter plate and blade root are required to have a minimum weld leg length. However, with laser seam welding, increasing the weld leg length correspondingly increases the weld penetration depth. This undesirably extends the heat-affected zone of the weld, which may form porous regions and cracks in the weld. Additionally, laser seam welds are difficult to visually evaluate if the meter plate is properly welded to the blade root. As such, there is a need for a welding process that provides good welds between metal parts (e.g., meter plates and blade roots), which are also easy to inspect.